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@uiten tstrs latrnt @frn Letters Patent No. 81,950, dated Septemer 8, 1868.

IMPROVEMENT IN BRIDGES.

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TO ALL WHOM IT MAY OONCERN:

Be it'kriown that we, HENRY A. Rusr and LUDWIG I-IERRMANN, ofvGhicago, inthe county of Cook, and State of Iliinois, have invented a new and useful Improvement lin Metal-lic Trusses for Bridges; and we do hereby declare and make known that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings, and the letters and figures marked thereon, which form part of this specification. j

Our said invention consists in a novel mode of securing the ends of the main braces in the top and bottom blocks, whereby provision is made for the variations in the position of the said braces incident upon the downward flexion of the bridge, as hereinafter more fully set forth. l A l Our said invention further consists in ar novel mode of securing the counter-braces in said top and bottom blocks, whereby said counter-braces ure caused automatically to tighten and brace the truss, when the downward iiexion ofthe bridge would relieve the counter-braces from action, and permitan upward movement orvibration to the bridge, after the weight causing the downward iiexion had been'removed.

To enable those skilled in the art to understand howto constructand use our said invention, we will describe the same with particularity,making reference in so doing to the aforesaid drawings, in which- Figure 1 represents a side elevation of a bridge'. I Figure 2 is an end view of the same. Figure 3 is a top view thereof, showing in part the top and in part the bottom chords.4 Figures 4 and 5 represent, respectively, a. side and edge view'ot one of the main braces. I" i a i are corresponding views of one of the counter-braces.

and 9 are corresponding views of the bars which form the bottom chords.

Figure 10 is av detailed perspective view of one of the bottom blocks, showing the mode of connecting the bars forming the bottom chords.

Figure l1 is a. vertical section through one ofthe bottom blocks, showing the mode of arranging the lower 4ends oi'4 the braces and counter-braces therein,

Figure 12 is a perspective view of one ofthe top blocks, and a section of the top chord, 'and Figure 13 is a. vertical central section through the parts represented in 5g. 12.

Similar letters of reference, in the several figures, denote the same parts of ourse.id invention.

A represents the bars which are employed in forming the bottom chords of the bridge, which are constructed with upset heads, a, as clearly shown in the drawings, or said heads may be formed by forging; The bottom blocks B are constructed in two sections, the lower ones being providedwith flanges, b b, as shown, which fit down upon each si'de of the tloorbeams, thus securing the said Hoor-beams firmly in their proper positions.

Across the lower face of the upper section, andthe upper face of the lower section, of said bottom blocks are formed four channels, to receive the bars A, which are arranged in place, and the top section of the block secured to the lower section, by means of the truss-bolts, and also the pressure ofthe braces, which rest upon :said blocks, :1s shown. The heads a prevent thebars from being withdrawn from the blocks,and thus the chord .is formed without the necessity of welding, or the use of bolts, pins, or rivets.

The .edges of the lchannels or grooves, in which the bars A are placed, are enlarged slightly, so as to per- :mit the bars to have verticai action, as the ,bridge has an upward or downward ilexion.

Byconstructing the bars A in the manner described, and connecting the same by meansof blocks, as specified, the risk of wea-keningthe chord by imperfect weldings, and the positive weakening of the same by 4boring or forming holes to receive pins, bolts, or rivets, is entirely avoided.

The main braces, which are marked C, may be constructed double7 as shown, or in any other suitable form, and have their upper andilower ends, c, made in a convex form, as shown in the drawings, and areentered in corresponding concave sockets, c, formed to receive and hold them firmly, but movably, in the top and bottom blocks, as shown, sothat their angles may change, to conform to the'varying position of the panel.

Instead of having bo'th ends ofsaid main braces madein a convex form, as specified, and havingboth Vends rest in the concave sockets c in the blocks, as described, one oi' said ends may be connected to its block by means of a pin, or be-xed in any other suitable manner thereto', the other dnd of the brace resting in a ooncave recess or socket, and being made convex, las described.

The object of this arrangement is to avoid rigidly attaching or xing the ends ofthe brace both to the top and'bottom chord, so that, when the bridge is exedfdownward by the passing *of a weight over it, the said brace, in being shortened, may have a movement to conform itselfl in position to the altered form of the panel, produced by said downward flexion, which result cannot be yattained when both ends of the braces are rigidly 'i attached or fixed to the upper `and lower chords, or to the-top and bottom blocks.

The lower ends, c, of the counter-braces, which are marked D, are constructed with convex or rounded bearings, and rest in corresponding concave recesses in'the bottom blocks, or said lower ends may be fixed to the block, but not rigidly. The upper ends, d', of said counter-braces, however, must be constructed with an inclination, substantially as shown, and must be ina corresponding inclined recess in the top block, F, which construction and arrangement are. clearly seen in figs. 6, 12, and 13.

The object of this feature of our invention is to render the counter-braces self-adjusting, so that, in the downward exion of 'the bridge, which'has the tendency to shorten the main braces, but to lengthen the counterbracesgor, rather, which has the tendency to throw the truss-panels from a rectangular to fa rhomboidal form, thus bringing the angles joined by the main brace nearer together, and moving the angles joined by the counterbraces (farther apart; the'said upper ends of the counter-braces will, from their own weight, slide down in the inclined socket cl, and thus hold the panel firmly braced, and prevent its swinging upwards, when the pressure,

, which caused the downward flexion, is moved, and thus the counter-brace is made to adjust itself under all circumstances, and keep the truss firmly and properly braced.

The braces and counter-braces, at the point where they cross each other, are connected by bolts passing through slots, shown in gs.' 4 and 6, which admits of the aforesaid change or movement of said braces and counter-braces, as desired.

The sections of the top chords F are secured in concave recesses in the sides of the top blocks, and have corresponding convex ends, so that, in the exion of the bridge, the requisite vertical action c'an be allowed in the chord, the edges of said recesses in the top blocks being made slightly daring, to allow said action.

Having described the construction and operation of our invention, we will specify what we claim, and desire t'o secure by Letters Patent.

1. We claim the arrangement of one or both ends of the main braces, when constructed in a convex or rounded form, in corresponding concave grooves or recesses in the blocks B and E, substantially as speciiied.

2. We claim the arrangement of the inclined end of the counter-braces in a corresponding inclined recess in the top block, to operate substantially as set' forth.

HENRY A. RUST,

L. HERRMANN.

Witnesses:

W. E. Manns, A. J. Cnoss. 

